Seedlings of the parasitic plant Cuscuta pentagona ( dodder) hunt by directing g
ID: 3302053 • Letter: S
Question
Seedlings of the parasitic plant Cuscuta pentagona (dodder) hunt by directing growth preferentially toward nearby host plants. Lacking eyes, or even a nervous system, how do they detect their victims? To investigate the possibility that the parasite detects volatile chemicals produced by host plants, Runyon et al. (2006) placed individual dodder seedlings into a vial of water at the center of a circular paper disc. A chamber containing volatile extracts from tomato (a host plant) in solvent was placed at one edge of the disc, whereas a control chamber containing only solvent was placed at the opposite end. The researchers divided the disc onto equal-area quadrants to record in which direction the seedlings grew. Of 30 dodder plants tested, 17 seedlings grew toward the volatiles, 2 grew away (toward the solvent), 7 grew toward the left side, and 4 grew toward the right side.
A. Graph the relative frequency distribution for these results. Which type of graph is ideal? Why?
B. What the relative frequencies expected if the parasite is unable to detect the plant volatiles or any other cues present? Include expected relative frequencies in graph for part A.
C. Using these data, calculate the fraciton of seedlings that grow toward the volatile. What does the fraction estimate?
D. Provide a standard error for your estimate. What does the standard error represent?
E. Calculate the of most-plausible values for the fraction of dodder seedlings that grow toward the volatiles under these experimental conditions. Does it include or exclude the fraction expected if the parasite is unable to detect plant volatiles or other cues present?
Show your work.
Explanation / Answer
N = 30 DODDER PLANTS TESTED.
Maximum plants are towards volatile.
type relative frequency A(towards volatile) 17/30 = 0.5666 56.66% B( towards solvent) 2/30 = 0.0666 6.66% C( LEFT SIDE) 7/30 = 0.2333 23.33% D( right side) 4/30 = 0.1333 13.33%